FR2771833A1 - Method of filtering to reduce pixel density deposited by printer - Google Patents

Abstract

The filtering method obtains a bidimensional pixel map of the image to be printed, and compares the value of a pixel with the values of the adjacent pixels. The value of this pixel is altered if a set number or adjacent pixel elements have the same value. The revised pixel map is then sent to the printer.

Description

Filtering method to reduce the pixel density
Correspondence with related request (s)
The present application claims priority, under USC 35 paragraph 119, of US Provisional Patent Application Serial No. 60 / 058,763, filed on the 12th
September 1997, the presentation of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION
The present invention relates to weft printer control devices for controlling printing machines and, more particularly, to a computer method that can be implemented on a weft printer control device to reduce the pixel density in a printer. areas of high pixel density of bit images before sending these binary images to the printing machines.

 Some printing machines or marking machines use non-impact printing technology known as magnetography. In a magnetography, a rotating metal drum is selectively magnetized by an array of small electromagnets to create a latent magnetic image on the drum. The drum is then exposed to magnetic toner particles, which are retained by the magnetized image areas of the drum. The image is then transferred to a substrate, such as paper, and is then fused to it. Commercially available marking machines using magnetographic technology include the Nipson M700 and 7000 series printers. A more detailed description of the magnetography process can be found in the Nipson web page "http://www.nipson.com/en/ magnetog, htm ".

 Single-color (ie, black-and-white) versions of such magneto-graphic printers receive binary images of printer drivers and, in turn, transfer the binary images onto the paper using the process. magnetograph described above. Such binary images are generally two-dimensional arrays of binary numbers, corresponding to the two-dimensional arrays of pixels to be transferred on the printed page. A binary number of positive value ("1") in the binary image corresponds to a full color pixel in the printed image, while a binary number of zero value ("0") in the binary image corresponds to one pixel empty or clear in the printed image.

 A known problem with the magnetographic method is that the intensity of the magnetic domains that are created on the imaging drum is not linear. Extremely dense areas in the image (areas in the image having a multitude of full color pixels packed together) will often leak the magnetic toner into less dense surrounding areas. Narrow bands of empty pixels surrounded by dense areas of full color pixels are particularly sensitive to this leakage effect.

 There is therefore a need for a means of reducing the density of solid color pixels in areas of full color at high density inside a binary image, before printing the image represented by the binary image, to compensate for the non-linear behavior of the magnetographic marking machine.

DfFINITIONS
For the purpose of this presentation, the following terms are defined as follows:
Pixel map: two-dimensional layout of elé
corresponding to a two-dimensional
pixels constituting a printed image.

Of course, a binary image is an example
a pixel map.

Positive value pixel element: an element of a
pixel map corresponding to a color pixel
full in the printed image. Represented so
characteristic by a binary "1" in an image
binary.

Zero value pixel element: an element of a
pixel map corresponding to an empty pixel or
clear in the printed image. Represented so
characteristic by a binary "0" in an image
binary.

SUMMARY OF THE INVENTION
The present invention provides a computer method that compensates for the non-linear behavior of magnetographic marking machines by reducing the density of solid color pixels in full-color, high-density areas within the image. The method can be implemented by the printer controller or by the marking machine itself, resulting in improved image quality. Preferably, the computer process also retains the less dense portions of the image.

In one embodiment of the present invention, a computer method for controlling the density of pixels deposited by a printing machine comprises the following steps: (a) obtaining a two-dimensional pixel map of a
image to print (b) select a first pixel element of value
positive in the pixel map (c) change the first pixel element to a value
null if a predetermined number of elements of
pixels in the pixel map immediately adja
cents to the first pixel element have a value
positive; and (d) send the pixel card to the printing machine
if we.

 In a preferred embodiment of this method, the predetermined number of pixel elements in the pixel map immediately adjacent to the first pixel element having a positive value must be equal to four (which corresponds to all immediately adjacent pixel elements). . Preferably, this method is implemented for each pixel element in the pixel map prior to shipping the pixel map to the printing machine. In addition, in various embodiments of the present invention, the borders of the high density pixel areas do not need to be subjected to the above test.

In another embodiment of the present invention, a computer method for controlling the density of pixels deposited by a printing machine comprises the following steps: (a) obtaining a two-dimensional pixel map of a
image to print (b) select a first pixel element of value
positive in the pixel map (c) assign a first weight to the pixel elements of
positive value in the immediate pixel map
adjacent to the first pixel element (d) to assign a second weight to the pixel elements of
positive value in the adjacent pixel map in
diagonal to the first pixel element (e) add together the first and second weights
assigned to obtain a total weight (f) change the first pixel element to a value
zero if the total weight is equal to or greater than one
predetermined threshold; and (g) send the pixel card to the printing machine
if we.

 In a preferred embodiment, the weight to be applied to the immediately adjacent positive pixel elements is "5", the weight applied to the diagonally adjacent positive pixel elements is equal to "1", and the threshold value is equal to either at "16" or at "17".

 It is therefore an object of the present invention to provide a computer method for reducing the positive pixel density in high density areas before transmitting the pixel map to the marking machine. It is another object of the present invention to keep the portions of the image less dense.

It is another object of the present invention to provide a computer method for controlling the pixel density deposited by a printing machine, which comprises the following steps: (a) obtaining a two-dimensional pixel map of a
image to print (b) compare the value of a first pixel element
in the pixel map to the values of the elements of
pixel adjacent to the first pixel element in the
pixel map (c) change the value of the first pixel element into
response to a determination, in the step of
comparison, that a predetermined number of elements
of pixels adjacent to the first pixel element have
the same value as the first pixel element; and (d) send the pixel card to the printing machine
if we.

 It is another object of the present invention that the above step of changing is performed in response to a determination, in the comparing step, that all pixel elements immediately adjacent to the first pixel element are the same. value as the first pixel element.

 It is another object of the present invention that the step of comparing comprises the steps of assigning a first weight to pixel elements immediately adjacent to the first pixel element and having the same value as the first pixel element assigning a second weight different from the first weight to the adjacent pixel elements diagonally to the first pixel element having the same value as the first pixel element, adding the weights of the immediately adjacent and diagonally adjacent pixel elements to obtain a total weight, and comparing the weight total to a predetermined threshold; and wherein the changing steps comprise the step of changing the value of the first pixel element in response to a determination, in the comparing step, that the total weight is equal to or greater than the predetermined threshold.

It is also an object of the present invention to provide a software program, stored in a memory device, configured to control a printer controller or marking machine to perform the following steps: (a) obtain a card of two-dimensional pixels of a
image to be printed (b) preparing a value of a first pixel element
in the pixel map with element values
of pixels adjacent to the first pixel element in
the pixel map; and (c) change the value of the first pixel element to
response to a determination, in the step of compa
reason, that a predetermined number of
pixel adjacent to the first pixel element have the
same value as this first pixel element.

 These and other objects and advantages of the present invention will become apparent from the following description, the accompanying drawings and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS - Figure 1 is a block diagram of a system
computer-controlled printing and incorporating
the present invention - Figure 2 is a representative illustration
of a pixel map - Figure 3 is a flowchart of a method of the
the present invention - FIG. 4 is a schematic flowchart of a
method of the present invention; and - Figure 5 is a flow diagram of another process
of the present invention.

DETAILED DESCRIPTION OF THE INVENTION
As seen in FIG. 1, an embodiment of a computer-controlled printing system 10 incorporating the method and system of the present invention includes a trunk, such as an ETHERNET line. , a controller for a high-speed printer 14 coupled to the ETHERNET line 12, an operator display console 16 coupled to the ETHERNET line, and at least one host or peripheral computer 18 coupled to the line
ETHERNET. The printer controller 14 is configured to receive from the network (e.g. by transmitting one of the computers 18), page description language ("PDL") files, and convert the PDL files to binary images. which are transmitted to one or more printing machines 20.

The operator display console 22 preferably uses a touch screen graphical user interface to allow a person to control or monitor the operations of the printer controller 14. For detailed descriptions of a high speed printer control device and printing system for use with the present invention, see US Patent Nos. 5,594,860, 5,729,665 and 5,740,338. .

 The printer controller 14 includes a processor operably coupled to a random access memory (RAM) 24. The operations of the controller 14 are controlled according to a computer program residing within the RAM 24. The processor 22 is also operably coupled to a nonvolatile memory 26 as is known to those skilled in the art. The non-volatile memory 26 can store a version of the program so that it can be transferred into the RAM 24 by operation of the controller 14. For purposes of the present invention, software incorporating the computer method of the present invention (described hereinafter) may reside within a computer (such as printer controller 14), or alternatively reside within a memory device, such as RAM 24 or the non-volatile memory 26. Such a memory device can also take the form of any read-only memory ("ROM") as known to those skilled in the art. Examples of suitable ROM devices include CD ROMs, hard disks, floppy disks, EEPROM devices, flash memory devices, tapes, and the like.

 As seen in Figure 2, an image 28 of a two-dimensional pixel map of an image is generally a two-dimensional array of pixel elements. The pixel maps transferred on the printed page are typically arranged in a multiplicity of scan lines 30, which are rows of pixel elements. For the purpose of this description, each pixel element P in a pixel map comprises four immediately adjacent pixel elements 32 and also four diagonally adjacent pixel elements 34.

 Fig. 3 shows a first method for reducing the density of solid color areas (i.e. areas in a pixel map having a multitude of positive value pixel elements very close to one another) at inside an image to compensate for the non-linear behavior of a marking machine. A software program residing in the RAM 24 of the printer controller 14 will be configured to control the printer controller 14 so as to perform the following steps: first, as shown in the function block 36, we obtain a pixel map of an image. Since, in this particular embodiment, the pixel elements on the borders of the pixel map will never be reset, since at least one immediately adjacent pixel element will always have a zero value, in a functional block 38 the first line scanning of the pixel map is skipped. Advancing to the function block 40, the next scan line is extracted from the pixel map.

In the function block 42, the program determines whether or not the scan line extracted from the pixel map is the last scan line and, if so, the process is completed and the program proceeds to the function block 44 If, in the function block 42, the program determines that the present scan line is not the last scan line in the pixel map, the program proceeds to the function block 46. In the function block 46, the program jumps the first pixel element of the scan line, because the first pixel element in a scan line is a border pixel element.

Advancing to function block 48, the program obtains the next pixel element in the scan line. In the function block 50, the program determines whether the present pixel element is the last pixel element in the scan line; and, if so, it returns to the function block 40 to extract the next scan line. If, in the function block 50, the program determines that the present pixel element is not the last pixel element in the scan line, the program proceeds to the function block 52. In the function block 52, the program determines whether yes or no the present pixel element is a pixel element of positive value. If the present pixel element is not a positive value pixel element, the program returns to the function block 48 to capture the next pixel element in the scan line. However, if the present pixel element is a positive value pixel element, the program advances to the function block 54.

In the function block 54, the program determines whether or not all immediately adjacent pixel elements are positive value pixel elements. If this is not the case, the program returns to the function block 48 to enter the next pixel in the scan line. However, if in the function block 54 the program determines that all immediately adjacent pixel elements are positive value pixel elements, the program then advances to the function block 56 to reset the present pixel element to a pixel element. of zero value. From the function block 56, the program returns to the function block 48 to extract the next pixel element in the scan line.

 As a result, the program extracts one scan line at a time, skipping the upper and lower scan lines, and it checks each of the pixel elements on the scan lines, skipping the terminal pixel elements, to determine whether or not there is reset the pixel element of a positive value pixel element (representing a full color pixel in the printed image) to a pixel element of zero value (representing an empty or clear pixel in the printed image) .

The following is an example of the operation of the first method described above. The notation for the example is: "[A, B]" represents a pixel
A on the scan line B and "X" represents a positive pixel element in the pixel map and a "0" represents a zero pixel element in the pixel map.

Given five scan lines of pixel elements that are mostly positive pixel elements, except for a small band of zero-valued pixel elements near the upper right side of the pixel map, shown as following

<tb> 0 <SEP> 123456789 <SEP>
<tb> 1 <SEP> XXX <SEP> XXX <SEP> O <SEP> XX <SEP>
<tb> 2 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 3 <SEP> XXX <SEP> XX <SEP> 000 <SEP> X <SEP>
<tb> 4 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X <SEP>
<tb> 5 <SEP> XXX <SEP> XXX <SEP> O <SEP> XX <SEP>
<Tb>
According to the method described above, and for each pixel element, the program examines the immediately adjacent pixel elements and, if all four immediately adjacent pixel elements are of positive value, the current pixel element is then reset to a pixel element of negative value. According to the above method, the first and last scan lines are skipped, the first and last pixel elements in each scan line are skipped, and any pixel element of zero value is skipped. By processing the second pixel element in the second scanning line, positive value pixel element [2,2], the immediately adjacent pixel elements [2,1], [3,2], [2,3] are examined. ] and [1,2]. Since all immediately adjacent pixel elements are positive, the pixel element [2,2] is then reset to a pixel element of zero value. The following table shows the appearance of the exemplary pixel map as an example after the steps above.

<Tb>

0 <SEP> 1 <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 6 <SEP> 7 <SEP> 8 <SEP> 9
<tb> 1 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> X <SEP> X
<tb> 2 <SEP> X <SEP> O <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 3 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 4 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 5 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> X <SEP> X
<Tb>
Then, processing the pixel element [3,2], the immediately adjacent pixel elements are [3,1], [4,2], [2,2] and [3,3]. Since the immediately adjacent pixel element [2,2] is now a pixel element of zero value, the present positive pixel element [3,2] is left unchanged. As a result, the pixel map after this step remains as follows

<tb> 0 <SEP> 123456789 <SEP>
<tb> 1 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> X <SEP> X
<tb> 2 <SEP> X <SEP> O <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 3 <SEP> XXX <SEP> XX <SEP> 000 <SEP> X <SEP>
<tb> 4 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 5 <SEP> XXX <SEP> XXX <SEP> 0 <SEP> XX <SEP>
<Tb>
Then, processing the pixel element [4,2], the immediately adjacent pixel elements are [4,1], [5,2], [4,3] and [3,2]. Since all these pixel elements immediately adjacent to the pixel are currently positive value pixel elements, the present pixel element [4,2] is reset to a pixel element of zero value. This results in the following aspect of the pixel map

<tb> 0 <SEP> 123456789 <SEP>
<tb> 1 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> X <SEP> X
<tb> 2 <SEP> X <SEP> O <SEP> X <SEP> O <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 3 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 4 <SEP> XXX <SEP> XX <SEP> 000 <SEP> X <SEP>
<tb> 5 <SEP> XXX <SEP> XXX <SEP> O <SEP> XX <SEP>
<Tb>
This process continues for all pixel elements on scan lines 2 to 5 except for the first and last pixel elements. At the end of this process, as seen in the following resulting pixel map, only pixel elements [2,2], [4,2], [3,3], [2,4] and [4] , 4] have been reset to a pixel element of zero value.

<Tb>

0 <SEP> 123456789 <SEP>
<tb> 1 <SEP> XXX <SEP> XXX <SEP> O <SEP> XX <SEP>
<tb> 2 <SEP> X <SEP> O <SEP> X <SEP> O <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 3 <SEP> X <SEP> X <SEP> O <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 4 <SEP> X <SEP> O <SEP> X <SEP> O <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 5 <SEP> XXX <SEP> XXX <SEP> O <SEP> XX <SEP>
<Tb>
As can be seen in FIG. 4, if the pixel map 28 is a bitmap having binary numbers of "1" corresponding to full color pixels and binary numbers of "0" corresponding to empty pixels, a version of the first method described above can be implemented in a hardware or software using a register or step of shifting to the right 58, a register or step of shifting to the left 60, a device or step of logical AND 62, a logical NO device or step 64 and a logic AND device or step 65. The right-shifting register or step 58 and the left-shift register or step 60 are adapted to receive a scan line of the card of pixels and shift respectively the scan line one digit to the right or to the left.

To process a particular pixel element P in the pixel map 28 using the hardware or software arrangement shown in FIG. 4, the following steps are performed: first, the scanning line 66 containing the present element P pixel is sent through the register or shift step to the right 58, the result of which is sent to the device or step AND 62; the present scan line 56 is also sent to the left-shift register or step 60, the result of which is sent to the device OR step AND 62. The previous scan line 68 is sent to the device or step
AND 62 and the next scan line 70 is also sent to the device or AND step 62. The logical AND device 62 produces a resultant scan line 72.

Then, the pixel element P 'in the resulting scan line 72, corresponding to the position of the present pixel element P in the present scan line 68, is sent through the device or step NO 64, the output of which is sent to an input of the device or step AND 65. The other input to the device or step AND 65 is the present pixel element P. Finally, the result of the device or step
ET 65 is then inserted in place of the present pixel element P in the pixel map 28.

 Referring to Fig. 5, there is shown a second method for reducing the density of solid color areas (i.e., areas in a pixel map having a multitude of positive value pixel elements in close proximity to each other. narrow of each other) within an image to compensate for the non-linear behavior of a marking machine. A software program residing in a RAM 24 of the printer controller 14 will be configured to control the printer controller 14 to perform the following steps: first, in a function block 74, the program gets the pixel map. Advancing to function block 76, the program will access the first scan line from the pixel map. Advancing to function block 78, the program will access the first pixel element in the scan line. Advancing to function block 80, the program will determine whether the present pixel element is a positive value pixel element. If the present pixel element is a positive value pixel element, the program will advance to the function block 82 and, if the present pixel element is a pixel element of zero value, the program will advance to the function block 84. In the block In operation 82, the program will apply a value weight "5" to all positive value pixel elements that are immediately adjacent to the present pixel element. Advancing to function block 86, the program will apply a value weight "1" to all adjacent positive pixel elements diagonally to the present pixel element. Advancing to function block 88, the program will sum together all weights applied to immediately adjacent and diagonally adjacent pixel elements from steps 82 and 86 to determine the total weight. Advancing to function block 90, the program will compare the calculated total weight in function block 88 with a threshold value. If the total weight is greater than or equal to the threshold value, the program will advance to function block 92; but, if the total weight is not equal to or greater than the threshold value, the program will advance to function block 84. It has been found that the threshold values of 16 or 17 seem well suited to the Nipson 700 printing machine. However, those skilled in the art will be able to experiment with other threshold values to determine which are the best threshold values for a particular application.

In the function block 92, since the total weight calculated in the function block 88 is greater than or equal to the threshold, the program will reset the present pixel element to a pixel element of zero value and then advance to the function block 84. Function block 84, the program will determine whether or not the present pixel element is at the end of a scan line. Otherwise, the program will advance to the function block 94 to obtain the next pixel element of the scan line and then return to the function block 80. If in the function block 84 the program determines that the present pixel element is in the end of the scan line, then the program will advance to function block 96 to determine whether or not the present scan line is the last scan line. If the present scan line is not the last scan line, then program to the function block 98 to enter the next scan line in the pixel map and, from the function block 98, the program will return to the function block 78. If, in the function block 96, the program determines that the present scan line is the last scan line in the pixel map, then the process is completed and the program proceeds to the function block 100. It should be noted that in this case second method, the first and last scan lines, as well as the first and last pixel elements in each scan line are not skipped.

The following is an example of the second method described in FIG. 5, implemented on the same pixel map as in the previous example, which is the following

<tb> 0 <SEP> 1 <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 6 <SEP> 7 <SEP> 8 <SEP> 9
<tb> 1 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> X <SEP> X
<tb> 2 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 3 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 4 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 5 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> X <SEP> X
<Tb>
In this example, the threshold value is set to 16. When processing element [1,1], weights are applied and added as shown in the following table

<tb> Element <SEP> of <SEP> pixel <SEP> Value <SEP> Weight <SEP> Value <SEP> weighed
<tb> [1,0] <SEP> Null <SEP> 5 <SEP> 0
<tb> [2,0] <SEP> Null <SEP> 1 <SEP> 0
<tb> [2.1] <SEP> Positive <SEP> 5 <SEP> 5
<tb> [2,2] <SEP> Positive <SEP> 1 <SEP> 1
<tb> [1,2] <SEP> Positive <SEP> 5 <SEP> 5
<tb> [0,2] <SEP> No <SEP> 1 <SEP> 0
<tb> [0,1] <SEP> Null <SEP> 5 <SEP> 0
<tb> [0,0] <SEP> Null <SEP> 1 <SEP> 0
<tb><SEP> Sum <SEP> =
<tb><SEP> weighted <SEP>: <SEP> 11
<Tb>
Using a threshold value of 16 would cause this pixel element to remain a positive pixel element. By processing the next pixel element in the scan line, the pixel element [2,1], the weights are applied and summed as seen in the following table.

<tb> Element <SEP> of <SEP> pixel <SEP> Value <SEP> Weight <SEP> Value <SEP> weighed
<tb> [2,0] <SEP> Null <SEP> 5 <SEP> 0
<tb> [3,0] <SEP> Null <SEP> 1 <SEP> 0
<tb> [3.1] <SEP> Positive <SEP> 5 <SEP> 5
<tb> [3,2] <SEP> Positive <SEP> 1 <SEP> 1
<tb> [2,2] <SEP> Positive <SEP> 5 <SEP> 5
<tb> [1,2] <SEP> Positive <SEP> 1 <SEP> 1
<tb> [1,1] <SEP> Positive <SEP> 5 <SEP> 5
<tb> [1,0] <SEP> No <SEP> 1 <SEP> 0
<tb><SEP> Sum
<tb><SEP> weighted <SEP>: <SEP> 17
<Tb>
Using a threshold value of 16 would cause this pixel element to be reset to a zero pixel value, which would result in the next pixel map at that time

<tb> 0 <SEP> 123456789 <SEP>
<tb> 1 <SEP> X <SEP> Y <SEP> XXX <SEP> X <SEP> Y <SEP> XX <SEP>
<tb> 2 <SEP> XXX <SEP> XX <SEP> 000 <SEP> X <SEP>
<tb> 3 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 4 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 5 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> X <SEP> X
<Tb>
Processing the remaining pixel elements in the first scan line, one by one, in the same way, would yield the next pixel map

<tb> 0 <SEP> 123456789 <SEP>
<tb> 1 <SEP> X <SEP> O <SEP> X <SEP> Y <SEP> XX <SEP> Y <SEP> XX <SEP>
<tb> 2 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 3 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 4 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 5 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> X <SEP> X <SEP>
<Tb>
And finally, the treatment of the remaining scan lines, one by one, in the same way as the first scan line, would yield the following pixel map

<tb> 0 <SEP> 1 <SEP> 2 <SEP> 3 <SEP> 4 <SEP> 5 <SEP> 6 <SEP> 7 <SEP> 8 <SEP> 9
<tb> 1 <SEP> X <SEP> O <SEP> X <SEP> O <SEP> X <SEP> X <SEP> O <SEP> X <SEP> X
<tb> 2 <SEP> O <SEP> X <SEP> O <SEP> X <SEP> O <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 3 <SEP> X <SEP> O <SEP> X <SEP> O <SEP> X <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 4 <SEP> O <SEP> X <SEP> O <SEP> X <SEP> O <SEP> O <SEP> O <SEP> O <SEP> X
<tb> 5 <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> X <SEP> O <SEP> X <SEP> X
<Tb>
It will be understood that modifications may be made to any of the foregoing embodiments without departing from the scope of the present invention as defined in the following claims. For example, in one of the above methods, it is within the scope of the present invention to process each second, third or fourth pixel element in the scanning line, rather than treating each pixel on a scan line. . Likewise, it is within the scope of the present invention to process each second, third or fourth scan line in this manner.

Claims (16)

 if we.  same value as the first pixel element; and ship the pixel card to an impres machine  pixel adjacent to the first pixel element have the  reason, that a predetermined number of  response to a determination, in the step of compa  pixel map change the value of the first pixel element in  pixel adjacent to the first pixel element in the  in the pixel map to element values of  image to print; compare a value of a first pixel element  A computer method for controlling the density of pixels deposited by a printing machine, comprising the steps of obtaining a two-dimensional pixel map of a  The computer method of claim 1, wherein the step of changing is performed in response to a determination, in the comparing step, that all pixel elements immediately adjacent to the first pixel element have the same value as the first pixel element.  The computer method of claim 2, wherein the value of the first pixel element is a positive value and the changing step changes the value of the first pixel element to a zero value.  4. A computer method according to claim 3, wherein the positive value corresponds to a color pixel deposited by the printing machine and in which the zero value corresponds to no pixel deposited by the printing machine.  The computer method of claim 1, wherein the comparing step comprises the steps of assigning a first weight to the pixel elements.  immediately adjacent to the first pixel element  having the same value as the first element of  pixel, assign a second different weight to the  first weight to the adjacent pixel elements in  diagonal to the first pixel element having the same  value as the first pixel element, add  the weights of pixel elements immediately  adjacent and diagonally adjacent to obtain a  total weight, and compare the total weight to a threshold  predetermined; and - the step of change includes the step in  which one changes the value of the first element of  pixel in response to a determination, in the step  comparison, that the total weight is equal or  greater than the predetermined threshold.  The computer method of claim 5, wherein the first weight is about five times the second weight.  The computer method of claim 1, wherein the comparing and changing steps are sequentially repeated for each pixel element in the pixel map.  The computer method of claim 1, wherein the comparing and changing steps are sequentially repeated for each pixel element in the pixel map except for the border pixel elements.  The computer method of claim 1, wherein the comparing and changing steps are sequentially repeated for each predetermined number of pixel elements in the pixel map.  if we.  resultant has a positive value; and ship the pixel card to an impres machine  in the first position in the scan line  pixel map if a pixel element lying  resultant - reset the first pixel element in the  binary, to produce a scan line  sweeping shifted to the right of a number  of a binary number and the first line of  first scan line shifted to the left  immediately the first scan line, the  scan, a third scan line next  immediately preceding the first line of  scan line, a second scan line  scan line - perform a logical AND operation on the first  finding at a first position in the first  pixel map, the first pixel element is  multiplicity of scan lines - select a first pixel element in the  image to print, the pixel map having a  A computer method for controlling the density of pixels deposited by a printing machine, comprising the steps of obtaining a two-dimensional pixel map of a  if we.  and ship the pixel card to an impres machine  first pixel element have a positive value  in the pixel map immediately adjacent to the  null if a predetermined number of pixel elements  positive in the pixel map change the first pixel element into a value  image to print; - select a first pixel element of value  11. A computer method for controlling the density of pixels deposited by a printing machine, comprising the steps of obtaining a two-dimensional pixel map of a  12. The computer method of claim 11, wherein the predetermined number is four.  if we.  predetermined threshold; and ship the pixel card to an impres machine  zero if the total weight is equal to or greater than one  assigned to get a total weight change the first pixel element into a value  diagonally to the first pixel element - add the first and second weights together  positive value in the adjacent pixel map  adjacent to the first pixel element assign a second weight to the pixel elements of  positive value in the immediate pixel map  positive in the pixel map assign a first weight to the pixel elements of  image to print - select a first pixel element of value  13. A computer method for controlling the density of pixels deposited by a printing machine, comprising the steps of obtaining a two-dimensional pixel map of a  14. The computer method of claim 13, wherein the first weight is larger than the second weight.  The computer method of claim 14, wherein the first weight is five times the second weight.  16. A computer method according to claim 15, wherein the first weight is 1, the second weight is 5 and the predetermined threshold is between 16 and 19.